Three people have been arrested by gardaí investigating the murder of Michael Keogh in May of 2017.
The 37-year-old was shot dead in an underground car park at Sheridan Court on Dorset Street, in Dublin's north inner city.
The killing is thought to be linked to the Hutch-Kinahan feud.
Gardaí are questioning two men in their 40s and a woman in her 30s.
One of the men and the woman are being held under Section 50 of the Criminal Justice, 2007.
The other man is detained under Section 4 of the Criminal Justice Act, 1984.
They're all being held at city centre Garda Stations in Dublin.